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Ex_9_8.sce

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+//This Source file is written by Nikita Rath (18BLC1131)
+clear;
+exec("F:\APP MAIN\Scilab\Ex_9_8_lru.sci")
+exec("F:\APP MAIN\Scilab\Ex_9_8_fifo.sci")
+exec("F:\APP MAIN\Scilab\Ex_9_8_optimal.sci")
+clc;
+
+//MAIN: (Given Conditions)
+printf("\n Given Page Reference String :\n \t")
+n = 20
+a = [1 2 3 4 2 1 5 6 2 1 2 3 7 6 3 2 1 2 3 6]
+for i = 1:n
+    printf("%d ",a(i)) 
+end
+
+printf("\n\n  1) LRU replacement :\n\n")
+lru(a,n)
+
+printf("\n  2) FIFO replacement :\n\n")
+fifo(a,n)
+
+printf("\n  3) Optimal replacement :\n\n")
+op(a,n)

Ex_9_8_fifo.sci

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+//This Source file is written by Nikita Rath (18BLC1131)
+//FUNCTION FOR FIFO
+function [] = fifo(a,n)
+    printf("\tNo. of Frames \t FIFO")
+    x = 1
+    //for frames 1 to 7
+    while(x < 8)
+        counter = 0
+        faults = 0
+        //Intialise all frames to -1
+        for i = 1:x
+            frames(i) = -1
+        end
+        flag1 = 1
+        //Traversing through pages
+        for i = 1:n
+            counter = 0
+            //Traversing through frames
+            for k = 1:x
+                //Page available in frame
+                if(frames(k) == a(i)) then
+                    counter = counter + 1
+                end
+            end
+            //Page unavailable in frame
+            if(counter == 0) then
+                //First in page gets replaced first in frame
+                frames(flag1+1) = a(i)
+                flag1 = modulo((flag1+1),x)
+                //Increment page faults
+                faults = faults + 1
+            end
+        end
+        //Total page faults
+        printf("\n\t\t %d \t %d ", x, faults)
+        x = x + 1
+    end
+    printf("\n")
+endfunction

Ex_9_8_lru.sci

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+//This Source file is written by Nikita Rath (18BLC1131)
+//FUNCTION FOR LRU
+function [] = lru(a,n)
+    printf("\tNo. of Frames \t LRU")
+    x = 1
+    //for frames 1 to 7
+    while(x < 8)
+        counter = 0
+        faults = 0
+        //Intialise all frames to -1
+        for i = 1:x
+            frames(i) = -1
+        end
+        //Traversing through pages
+        for i = 1:n
+            flag1 = 0 
+            flag2 = 0
+            //Traversing through frames
+            for j = 1:x
+                //Page available in frame 
+                if(frames(j) == a(i)) then
+                    counter = counter + 1
+                    temp(j) = counter
+                    //Set flag1 and flag2
+                    flag1 = 1
+                    flag2 = 1
+                    break
+                end
+            end
+            //Page unavailable in frame
+            if(flag1 == 0) then
+                //Traversing through frames
+                for j = 1:x
+                    //Frame has empty space
+                    if(frames(j) == -1) then
+                        counter = counter + 1
+                        //Increment page faults
+                        faults = faults + 1
+                        frames(j) = a(i)
+                        temp(j) = counter
+                        flag2 = 1
+                        break
+                    end
+                end
+            end
+            //Page unavailable in frame
+            if(flag2 == 0) then
+                minimum = temp(1)
+                pos = 1
+                //Traversing through frames
+                for k = 2:x
+                    //Find least recently used page
+                    if(temp(k) < minimum) then
+                        minimum = temp(k)
+                        pos = k
+                    end
+                end
+                counter = counter + 1
+                //Increment page faults
+                faults = faults + 1
+                frames(pos) = a(i)
+                temp(pos) = counter
+            end
+        end
+        //Total page faults
+        printf("\n\t\t %d \t %d ", x, faults)
+        x = x + 1
+    end
+    printf("\n")
+endfunction

Ex_9_8_optimal.sci

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+//This Source file is written by Nikita Rath (18BLC1131)
+//FUNCTION FOR OPTIMAL
+function [] = op(a,n)
+    printf("\tNo. of Frames \t Optimal")
+    x = 1
+    //for frames 1 to 7
+    while(x < 8)
+        counter = 0
+        faults = 0
+        //Intialise all frames to -1
+        for i = 1:x
+            frames(i) = -1
+        end
+        //Traversing through pages
+        for i = 1:n
+            flag1 = 0
+            flag2 = 0
+            //Traversing through frames
+            for j = 1:x
+                //Page available in frame
+                if(frames(j) == a(i)) then
+                    //Set flag1 and flag2
+                    flag1 = 1
+                    flag2 = 1
+                    break
+                end
+            end
+            //Page unavailable in frame
+            if(flag1 == 0) then
+                //Traversing through frames
+                for j = 1:x
+                    //Frame has empty space
+                    if(frames(j) == -1) then
+                        //Increment page faults
+                        faults = faults + 1
+                        frames(j) = a(i)
+                        flag2 = 1
+                        break
+                    end
+                end
+            end
+            //Page unavailable in frame
+            if(flag2 == 0) then
+                flag3 =0
+                //Traversing through frames
+                for j = 1:x
+                    temp(j) = -1
+                    //Traversing through future pages
+                    for k = i+1:n
+                        //Page currently in frame available in future pages
+                        if(frames(j) == a(k)) then
+                            temp(j) = k
+                            break
+                        end
+                    end
+                end
+                //Traversing through frames
+                for j = 1:x
+                    //page currently in frame unavailable in future pages
+                    if(temp(j) == -1) then
+                        pos = j
+                        //Set flag3
+                        flag3 = 1
+                        break
+                    end
+                end
+                //Page currently in frame available in future pages
+                if(flag3 ==0) then
+                    maximum = temp(1)
+                    pos = 1
+                    //Traversing through frames
+                    for j = 2:x
+                        //Find page in frame which is farther in future pages
+                        if(temp(j) > maximum) then
+                            maximum = temp(j)
+                            pos = j
+                        end
+                    end
+                end
+                frames(pos) = a(i)
+                //Increment page faults
+                faults = faults + 1
+            end
+        end
+        //Total page faults
+        printf("\n\t\t %d \t %d ", x, faults)
+        x = x + 1
+    end
+    printf("\n")
+endfunction